REACTION-SINTERING PROCESS FOR CALCIUM-DOPED LANTHANUM CHROMITE INTERCONNECT CERAMICS OF SOLID OXIDE FUEL CELL Yi-Cheng Liou*, Wen-Chou Tsai, Chii-Shyang Huang Department of Electronics Engineering, Kun Shan University, Tainan Hsien 71003, Taiwan, R.O.C. *Corresponding author. Calcium-doped lanthanum chromite La 0.7 Ca 0.31 CrO 3 (LCC) interconnect ceramics of solid oxide fuel cells prepared using a reaction-sintering process were investigated. Without any calcination involved, the mixture of La 2 O 3, CaCO 3, and Cr 2 O 3 was pressed and sintered directly. Shrinkage percentage increased from 8-9% at 1100 o C to 26-27% at o C. Density increased with sintering temperature and reaches a maximum value 6.01 g/cm 3 at 1300 o C/6 h. Results indicate that reaction-sintering process could be a proper approach to prepare LaCaCrO 3 ceramics for interconnects in solid oxide fuel cells. Fig.1 shows the XRD patterns of the LCC ceramics sintered at 1100 o C to 1300 o C for 6 h. All the diffraction peaks match the ones of ICDD PDF # (La 0.7 Ca 0.3 CrO 3 ) and no second phases were found even for the sample sintered at 1100 o C. Therefore, the reaction-sintering process is proven effective in preparing LCC ceramics. This simple process is effective not only in preparing BaTi 4 O 9, Ba 5 Nb 4 O 15, Sr 5 Nb 4 O 15, CaNb 2 O 6, NiNb 2 O 6 and Pb-based complex perovskite ceramics but also effective in preparing LCC ceramics. SEM photographs of the LCC ceramics sintered at 1100 o C to 1300 o C for 2 h are shown in Fig. 2. At sintering temperature lower than 1200 o C, the ceramics are porous and loosely constructed. At sintering temperature over 1200 o C, we found some grains of rectangular, thin slice, or other shapes. Less porosity is found and grains began to grow and the ceramics were under densification. However, the dominant outline of LCC grains is not clear and the grains grow mildly in size with increasing sintering temperature. Fig. 3 shows SEM photographs of the LCC ceramics sintered at 1100 o C to 1300 o C for 6 h. These figures illustrated a similar grain growing phenomena to that for 2 h, that is, the LCC ceramics sintered below 1200 o C are porous and loosely constructed and the grains grow mildly in size with increasing sintering temperature. Thus an increase of soaking time does not result in much bigger grain size. Shrinkage percentage of LCC ceramics increased from 8-9% at 1100 o C to % at o C as shown in Fig. 4. The figure reveals that a temperature of 1200 o C is high enough for densification of LCC ceramics. Fig. 5 shows the density of the LCC ceramics sintered at 1100 o C to 1300 o C for 2-6 h. The density increases linearly with increasing sintering temperatures up to 1200 o C. At sintering temperature over 1200 o C, the density saturated around 6 g/cm 3 regardless of the 2-6 h soaking time. The highest density is 6.01 g/cm 3 for samples sintered at 1300 o C for 6 h, which corresponds to a relative density of 98.8% if a theoretical density g/cm 3 of La 0.7 Ca 0.3 CrO 3 is used. In La 0.9 Ca 0.1 CrO 3 and La 0.8 Ca 0.2 CrO 3 prepared using hydrothermal method and sintered at 1400 o C for 5 h, Rivas-Vázquez and co-workers reported a relative density of 96.8% and 97.7% was obtained, respectively. Since interconnects in solid oxide fuel cells need to be of high density, our reaction- sintering process could be a suitable approach in preparing dense LCC ceramics. Fig. 1 XRD patterns of the LCC ceramics with 1wt ％ B 2 O 3 addition and sintered at o C for 6h. (La 0.7 Ca 0.3 CrO 3 : ICDD PDF # ) Fig. 4 Shrinkage percentage of LCC ceramics sintered at various temperatures and soak time. Fig. 5 Density of LCC ceramics sintered at various temperatures and soak time. Fig. 2 SEM photographs of the LCC ceramics sintered at (A) 1100 o C, (B) 1150 o C, (C)1200 o C, (D) 1250 o C, and (E)1300 o C for 2 h. Fig. 3 SEM photographs of the LCC ceramics sintered at (A) 1100 o C, (B) 1150 o C, (C)1200 o C, (D) 1250 o C, and (E)1300 o C for 6 h. Materials and Austceram 2007 July 4 - 6, 2007, Sydney, Australia